Inverse Trans Influence in Low-Valence Actinide ... - ACS Publications

Article Cite This: Inorg. Chem. XXXX, XXX, XXX−XXX

pubs.acs.org/IC

Inverse Trans Influence in Low-Valence Actinide−Group 10 Metal Complexes of Phosphinoaryl Oxides: A Theoretical Study via Tuning Metals and Donor Ligands Raza ullah shah Bacha, Yan-Ting Bi, Li-Chun Xuan,* and Qing-Jiang Pan* Key Laboratory of Functional Inorganic Material Chemistry (Ministry of Education), School of Chemistry and Materials Science, Heilongjiang University, Harbin 150080, China Downloaded via BUFFALO STATE on July 18, 2019 at 13:24:18 (UTC). See https://pubs.acs.org/sharingguidelines for options on how to legitimately share published articles.

S Supporting Information *

ABSTRACT: The recognition and in-depth understanding of inverse trans influence (ITI) have successfully guided the synthesis of novel actinide complexes and enriched actinide chemistry. Those complexes, however, are mainly limited to the involvement of high-valence actinide and/or metal−ligand multiple bonds. Examples containing both low oxidation state actinide and metal−metal single bond remain rare. Herein, more than 20 actinide-transition metal (An-TM) complexes of phosphinoaryl oxide ligands have been designed in accordance with several experimentally known analogs, by changing the metal atoms (An = Th, Pa, U, Np, and Pu; and TM = Ni, Pd, and Pt), actinide oxidation states (IV and III) and metal−metal axial donor ligands (X = Me3SiO, F, Cl, Br, and I). The relativistic density functional theory study of structural (trans-An−X and cis-An−O toward An−TM), bonding (topological electron/energy density), and electronic properties reveals the order of the ITI stabilizing actinide−metal bond. Computed electron affinity (EA) values, related to the electrochemical reduction, linearly correlate with experimentally measured reduction potentials. Although the same ITI order for the ligand donors was shown as in a previous study, the correlation between electrochemical reduction and the ITI was found to be weak when the actinide atoms were changed. For most complexes, the reduction is primarily of an actinide-based mechanism with minor participation of transition metal and phosphinoaryl oxide, whereas that of thorium−nickel complexes is different.

1. INTRODUCTION An inverse trans influence (ITI)1−3 has been applied to rationalize the outstanding thermodynamic stability of linear uranyl (UO22+) species, which is the most prevalent in the nuclear-fuel cycle.4−8 Unlike a trans influence that weakens mutually trans metal−ligand bonds, the ITI reinforces them via a synergistic thermodynamic stabilization. Regarding high oxidation state actinides, the ITI origin was attributed to the mixing of vacant 5f and semicore 6p orbitals by Denning et al.; 1,2 later, a comprehensive study of O’Grady and Kaltsoyannis concluded that the actinide 6p semicore orbitals did affect ITI but were not the only determining factor.3 The recognition of ITI has advanced synthesis of numerous novel actinide complexes that are supposed to be unstable.9−15 For example, the stability of the uranium−carbon bond in (OUVIX)[N(SiMe3)2]3 (X = −CH3 and −CCPh) was attributed to an ITI, where the hydrocarbyl group was trans to the UO multiple bond.14 So far, most complexes reported are limited to high-valence actinides (such as the uranyl cation and its imido analogs) and/or involving metal−ligand multiple bonds. Recently, Liddle and co-workers have found the ITI in tetravalent uranium and thorium bis(carbene) complexes and proposed that it may be a more general f-block principle.15 Inspired by these studies, in this work we will first extend ITI © XXXX American Chemical Society

to even lower oxidation state actinide (i.e., + III) and to transuraniums such as neptunium and plutonium. Second, ITI will be systematically explored to stabilize relatively weak actinidemetal single bond via manipulating trans-donor ligand as well as metal centers. Third, we endeavor to build the relationship of ITI with some important molecular properties. Up to date, uranium and thorium have been commonly applied to fabricate heterobimetallic actinide-metal complexes, where the other metal includes transition metal (TM) such as Ni,16−18 Pd,16 Pt,16 Cu,18,19 Ag,20 Co,17,21−23 Rh,24,25 Fe,26−32 Ru,28,33 Re34−36 and Mo37 and main group metal (MM) like Al,38,39 Ga,39,40 Ge,41 Sn,42,43 Sb44 and Bi.44 Most cases involve tetravalent actinide (An), but are rare for trivalent ones. In these complexes, a possible strategy of stabilizing the weak AnTM bond is to coordinate actinide with a trans donor ligand (X); when an ITI operates, X-An and An-TM are anticipated to reinforce each other. For example, complexes (IUIVTM0)(LE)3 (TM = Ni, Pd and Pt)16 have been successfully synthesized (LE = 2-tert-butyl-4-methyl-6(diphenylphosphino)phenolate). Substituting iodide afforded two more complexes (XUIV−Ni0)(LE)3 (X = F and Me3SiO). Received: April 23, 2019

A

DOI: 10.1021/acs.inorgchem.9b01193 Inorg. Chem. XXXX, XXX, XXX−XXX

Article

Inorganic Chemistry

mental media (gas phase and solution), electron-spin states, and theoretical approaches has been evaluated recently.50 The optimal ones were used in the present work. Specifically, the simplified ligand, 2-methyl-6-(dimethylphosphino)phenolate (marked as L), was used to replace the real experimental LE, the structure was optimized in the gas phase, and the highest electron-spin state was centered on. Regarding the theoretical approach that was verified to suit the current calculations, actinide and group 10 metal atoms were treated with Stuttgart relativistic small-core effective core potentials and associated valence basis sets;52 Hay-Wadt pseudopotentials and LANL08d basis sets were used for I, Br, Cl, and Si;52,53 all-electron Pople’s basis sets, 6-31G**, were employed for P, F, O, C, and H. Perdew−Burke−Ernzerhof (PBE)53 functional, a generalized gradient approximation (GGA), was applied. Comparison with meta-GGA TPSS and hybrid B3LYP shows that the GGA-PBE is sufficiently reliable and accurate for the current calculations.50 On the basis of the An−TM and An−X bonds using an electron density-based approach, the quantum theory of atoms in molecule (QTAIM).54,55 Using the Multiwfn code,56 we obtained QTAIM parameters [electron density ρ(r), Laplacian electron density ∇2ρ(r), energy density H(r)], as well as the ellipticity ε and delocalization index δ at bond critical points (BCPs). Energy density, H(r), was composed of two parts, kinetic G(r) and potential V(r). The unit of QTAIM parameters is “a.u.”. We also used an empirical equation of interaction energy (Eint in eV), Eint = V(r)/2,57−59 to quantatitively characterize the An−TM/X bond strength.

The ITI was considered to be a possible factor for stabilizing the U-TM bond; however the lack of prepared complex samples brought forth no conclusion. In this respect, a theoretical study of systematically designed complexes is quite appealing; moreover, previous density functional theory (DFT) and wave function theory (WFT) yielded reliable results for molecular properties of An-TM complexes.16,20−27,30,31,33,34,36,45 Redox property is of great importance in the extraction and separation of actinide radionuclides, the reuse of nuclear spent fuel and the management of nuclear waste.4−8,46−49 Arnold and co-workers found that the reduction potential of (XUIVTM0)(LE)3 (X = OSiMe3, F and I; TM = Ni, Pd and Pt) correlated well with metal−metal bond strength.16 However, whether it shows a similar relationship with ITI was not explored in that work. Herein, more than 20 An-TM complexes were designed via changing metal sorts, actinide oxidation states and donor ligands in the metal−metal axial direction. The order of ITI stabilizing actinide-metal bond is presented. The relationship of ITI with electrochemical reduction is addressed as well as the reduction mechanism.

2. COMPUTATIONAL DETAILS In Table 1, we present chemical formulas and abbreviations of three kinds of actinide-group 10 metal complexes of bidentate phosphi-

3. RESULTS AND DISCUSSION 3.1. Structural Properties and ITI. Geometry Parameters. It is known that the ITI reinforces (shortens) metal− ligand bonds trans to each other via a synergistic thermodynamic stabilization. So we will first explore the relationship of bond lengths with ITI for XAn−TM and [XAn−TM]− while changing X (Me3SiO, F, Cl, Br, and I), An (Th, Pa, U, Np, and Pu) and TM (Ni, Pd, and Pt). Optimized bond lengths and angles are listed in Tables 2 and Table S1, respectively, and their structural picutures are presented in Figure 1. As seen in Table 2, optimizations on the series complexes XU−Ni show approximately increasing trends of both U−X and U−Ni distances in going from X = Me3SiO, F, Cl, Br to I. Angles of X−U−Ni were found in the range of 170° ∼ 176° (Table S1), indicating that the two bonds are trans to each other. With respect to the U−Ni bonds, the cis−U-O bond lengths decrease when the ligands X are changed. The same trend is also found in [XU−Ni]−. Now, one may question that the regular increase of U-X distances comes from the difference of covalent radii of different X atoms but not from ITI. To solve this, we use the formal shortness ratio (FSRA‑B).60 It is defined as FSRA−B = DA−B/(RA + RB), where DA−B is the optimized A−B distance, and RA and RB values are the atomic radii. In the current calculations, we apply atomic covalent radii calculated by Pyykkö.61 Still, the FSR value of trans-U−X bond increase as the respective U−Ni distance lengthens (Table 2). Accordingly, we plotted U−Ni distances (Dis.) of XU-Ni and [XU-Ni]− against Dis.(U-X), FSRU‑X and Dis.(U−O) in Figure 2. One can see a positive correlation of U−Ni with trans-U−X and a negative one with cis−U−O. The correlation coefficients (R2) for the least-squares linear regression range from 0.521 to 0.809. Hence, the analysis of geometry parameters suggests an order of ITI stabilization on U−Ni bond as Me3SiO > F > Cl > Br > I. Analyzing structural parameters (Table 2) optimized for [U−TM]n (n = 0 and −1) and An-Ni reveals that the ITI orders follow a trend of Ni > Pt

Table 1. Formulas and Abbreviations of Heterobimetallic Actinide-Group 10 Transition Metal Complexes (Molecules) And Their One-Electron Reduced Products (Anions) formulas

abbreviationsa

molecule

(XU−Ni)(L)3

XU−Ni

anion

[(XU−Ni) (L)3]− (IU−TM)(L)3 [(IU−TM) (L)3]− (IAn−Ni)(L)3

[XU−Ni]−

[(IAn−Ni) (L)3]−

[An−Ni]−

molecule anion molecule anion

variables X = Me3SiO, F, Cl, Br, and I

U−TM [U−TM]−

TM = Ni, Pd, and Pt

An−Ni

An = Th, Pa, U, Np, and Pu

a

The L ligand symbol is omitted in all abbreviations for clarity, and similar case for X = I.

noaryl oxide ligands (L). They are designed by changing the actinide metal (An = Th, Pa, U, Np, and Pu), transition metal (TM = Ni, Pd, and Pt) and axial donor ligand (X = Me3SiO, F, Cl, Br, and I) trans to the heterobimetallic bond. One-electron reduction of these molecules affords corresponding anions. In this work, neutral molecules (XAn− TM)(L)3 and monovalent anions [(XAn−TM)(L)3]− are labeled as XAn−TM and [XAn−TM]−, respectively. Molecular properties that may potentially correlate with ITI stability such as geometry parameters, natural bond orbital (NBO) charges, electron-spin density, bonding, and electronic structures will be intensively investigated. Addtionally, the mechanism of the electrochemical reduction will be addressed as well as its relationship with ITI. It is worth noting that several uranium−metal molecules and one anion have been studied in our recent work,50 where we focused on the metal−metal bond strength and absorption spectra. All the calculations were accomplished with the Gaussian 09 program.51 Full geometry optimizations of these complexes were performed without any symmetry constraint. The performance of various simplification models of phosphinoaryl oxide ligand, environB


Article

Inorganic Chemistry

Table 2. Optimized Bond Lengths (Å) And Their Formal Shortness Ratio (FSR)a of Heterobimetallic Actinide−Transition Metal Molecules and Anions complexes

An−TM

FSRAn−TM

An−X

FSRAn−X

(An−O)avg

FSRAn−O

(TM−P)avg

SiOU−Ni FU−Ni ClU-Ni BrU−Ni U−Ni [SiOU−Ni]− [FU−Ni]− [ClU−Ni]− [BrU-Ni]− [U−Ni]− U−Pd U−Pt [U−Pd]− [U−Pt]− Th−Ni Pa−Ni Np−Ni Pu−Ni

2.497 2.488 2.506 2.497 2.514 2.641 2.639 2.689 2.685 2.679 2.732 2.762 2.947 2.931 2.581 2.561 2.501 2.499

0.892 0.889 0.895 0.892 0.898 0.895 0.895 0.912 0.910 0.908 0.942 0.943 0.966 0.952 0.906 0.908 0.890 0.886

2.077 2.051 2.603 2.786 3.020 2.138 2.079 2.677 2.872 3.123 3.020 3.027 3.115 3.123 3.087 3.065 3.019 3.003

0.891 0.876 0.968 0.981 0.997 0.862 0.835 0.943 0.961 1.044 0.997 0.999 0.980 0.982 1.002 1.005 0.993 0.985

2.174 2.193 2.164 2.163 2.154 2.235 2.232 2.211 2.209 2.200 2.145 2.144 2.201 2.203 2.214 2.225 2.160 2.172

0.933 0.941 0.929 0.928 0.924 0.959 0.958 0.949 0.948 0.944 0.921 0.920 0.945 0.945 0.719 0.713 0.711 0.712

2.209 2.210 2.208 2.209 2.208 2.170 2.173 2.171 2.172 2.173 2.371 2.351 2.340 2.321 2.202 2.209 2.208 2.212

See the definition of FSR in the text. According to Pyykkö’s values,61 the AnVI radii of Th, Pa, U, Np, and Pu are 1.75, 1.72, 1.70, 1.71, and 1.72 Å, respectively. Corresponding AnIII radii were obtained by adding 0.15 Å. And those of other atoms were taken as 1.10 Å (Ni), 1.20 (Pd), 1.23 (Pt), 0.63 (O), 0.64 (F), 0.99 (Cl), 1.14 (Br), and 1.33 (I). a

Ni stabilization. Consequently, NBO charges support the ITI order of X from Me3SiO, F, Cl, Br, to I. The correlation between ITI and NBO charges also holds for the series complexes [XU−Ni]−, but does not for [U−TM]n and [An− Ni]n (n = 0 and −1). The possible reason may be that charge calculations are sensitive to many factors like basis sets, partition scheme, and theoretical method. In brief, our results of ITI orders agree with those in previous studies of (OUVIX)[N(SiMe3)2]3 (X = OMe, F, Cl, Br, and I)14 and [OAnX5]n+ (An = Pa, U, and Np; X = F, Cl, and Br),3 where the ITI stabilization of X is created trans to actinide-oxo multiple bond. The orders of OMe > F > Cl > Br > I and Np > U > Pa were established by combined theoretical and experimental investigations. 3.2. Bonding Properties and ITI. In this section, we exploit topological properties of bonds to study the ITI in lowvalence actinide−transition metal complexes. Given the origin of the ITI effect, the An−TM distance is capable of acting as a medium to relate the bonding properties with the ITI. Previous studies of actinide complexes indicated that QTAIM parameters at BCPs can classify bond types.62−72 Accordingly, calculated values, 0 < ρ(r) < 0.1, ∇2ρ(r) > 0, and H(r) < 0 in Table 3, reveal a TM → An dative bond. The possibility of assigning an electron-transfer bond is ruled out by electron-spin density calculations (Table S2). Moreover, TM− An is of single-bond character, corroborated by values of δ(An, TM) of 0.54−1.04 and ε of 0.004−0.062. While changing axial donor X, bimetallic distances of [XU− Ni]n (n = 0 and −1) correlate well with QTAIM data [ρ(r), ∇2ρ(r), V(r), G(r), and -G(r)/V(r)], δ and Eint at the U−Ni BCPs. As shown in Figures S1 and S2, the U−Ni distances are inversely proportional to computed topological (absolute) values. So the order of ITI stabilization is given as Me3SiO > F > Cl > Br > I. Additionally, QTAIM calculations also show the ITI order of Ni > Pt > Pd for [U−TM]n (n = 0 and −1). For the series An−-Ni (An = Th, Pa, U, Np, and Pu), it is interesting to build the relationship between An-Ni bond

Figure 1. Structures of [(XAn−TM)(L)3]n (labeled as [XAn−TM]n; X = Me3SiO, F, Cl, Br, and I; An = Th, Pa, U, Np, and Pu; TM = Ni, P, and Pt; n = 0 and −1; and L is a bidentate phosphinoaryl oxide). Most of them share (a) similar basic structure, except for (b) {[(Me3SiO)U−Ni](L)3}n, marked as [SiOU−Ni]n.

> Pd and Pu > Np > U > Pa > Th, respectively. Therein, FSR values were used to cancel the impact of the difference of metal atomic radii. NBO Charges. The ITI stabilization created by changing X, TM and An is further explored by the extent of cis-An−O destabilization with respect to An−Ni. The An−O destabilization, denoted by the increased bond polarity, can be qualitatively measured by the calculated NBO charge (Table S2). For example, of all molecules XU-Ni, SiOU-Ni was calculated to have the most positive charge QU (1.46) and the most negative Q3L (−0.82), indicating the largest polarity in U−-L bonds, the most cis-destabilization, and the largest U− C


Article

Inorganic Chemistry

Figure 2. Plots of optimized U−Ni distances (Dis. in Å) against Dis(U−X), FSRU−X and Dis(U−O)av, for [XU−Ni]n (X = Me3SiO, F, Cl, Br, and I; n = 0 and −1).

Table 3. Calculated QTAIM Data (in a.u.) at An−TM Bond Critical Points (BCPs) for Actinide−Transition Metal Complexes, Along with Ellipticity (ε), Delocalization Index (δ), and Interaction Energy Eint (in eV) complexes

ρ(r)

∇2ρ(r)

H(r)

V(r)

G(r)

−G(r)/V(r)

ε

δ (An, TM)

Eint

SiOU−Ni FU−Ni ClU−Ni BrU-Ni U−Ni [SiOU−Ni]− [FU−Ni]− [ClU−Ni]− [BrU−Ni]− [U−Ni]− U−Pd U−Pt [U−Pd]− [U−Pt]− Th−Ni Pa−Ni Np−Ni Pu−Ni

0.0691 0.0703 0.0679 0.0690 0.0670 0.0582 0.0590 0.0541 0.0545 0.0549 0.0605 0.0656 0.0436 0.0516 0.0624 0.0605 0.0677 0.0660

0.1796 0.1830 0.1699 0.1750 0.1627 0.1118 0.1123 0.0903 0.0917 0.0935 0.1195 0.1267 0.0719 0.0881 0.1327 0.1411 0.1762 0.2036

−0.0163 −0.0167 −0.0167 −0.0170 −0.0168 −0.0161 −0.0163 −0.0157 −0.0158 −0.0159 −0.0161 −0.0178 −0.0099 −0.0119 −0.0173 −0.0151 −0.0163 −0.0146

−0.0775 −0.0792 −0.0760 −0.0777 −0.0743 −0.0601 −0.0608 −0.0541 −0.0546 −0.0551 −0.0620 −0.0672 −0.0377 −0.0457 −0.0678 −0.0655 −0.0767 −0.0802

0.0612 0.0625 0.0592 0.0607 0.0575 0.0440 0.0444 0.0383 0.0388 0.0393 0.0459 0.0494 0.0279 0.0338 0.0505 0.0504 0.0604 0.0655

0.7897 0.7891 0.7789 0.7812 0.7739 0.7321 0.7303 0.7079 0.7106 0.7132 0.7403 0.7351 0.7401 0.7396 0.7448 0.7695 0.7875 0.8167

0.0217 0.0151 0.0296 0.0295 0.0328 0.0600 0.0478 0.0621 0.0544 0.0502 0.0343 0.0360 0.0625 0.0624 0.0128 0.0072 0.0043 0.0042

1.0093 0.9970 0.9707 0.9798 0.9565 0.7529 0.7701 0.7091 0.7100 0.7176 0.7554 0.8192 0.5368 0.6463 0.7793 0.8867 0.9839 1.0330

−1.055 −1.077 −1.033 −1.057 −1.012 −0.818 −0.827 −0.736 −0.743 −0.750 −0.843 −0.915 −0.513 −0.622 −0.923 −0.891 −1.044 −1.091

where R2 is 0.927 and 0.914, respectively (Figures S4 and S5); a slightly smaller R2 values of 0.717 and 0.826 are fitted for δ(An, Ni) against SNi. No good linear correlation is observed for [XU-Ni]− in Figure S6. Interestingly, Eint linearly correlates with the spin density of each fragment of An-Ni, where fitted R2 values fall within 0.527 and 0.802 (Figure S7). 3.3. Electronic Properties and ITI. Adequate understanding of electronic structures of complexes could provide insights into the nature of the ITI. Energetic levels of α-spin occupied orbitals of XU-Ni are given in Figure 4. Notably, we focused on orbitals with metal-involved character and marked them with different-color solid lines. One can see that XU-Ni all have four types of metal-character orbitals. First is highlying orbitals of HOMO and HOMO−1 that are U(5f)-

strength and bonding properties. Because of the difference of various actinide elements in radius, FSRAn−Ni is preferred to denote the bond strength. As seen in Figure 3, FSRAn−Ni is correlated well with QTAIM data, δ(An, Ni) and Eint. The linear correlation coefficients R2 are fitted between 0.589 and 0.963. Interestingly, the linear correlation is also good when we use Dis.(An−Ni) instead for the fitting (Figure S3). Generally, the An−Ni bond strength is demonstrated to increase from Th to Pu. To connect with ITI, the order of Pu > Np > U > Pa > Th is proposed. Like bond length and FSR, delocalization index δ and interaction energy Eint are able to indicate bond strength. Regarding XU-Ni and An-Ni, we find that δ(An, Ni) correlates well with electron-spin density of uranium (SU) in Table S2, D


Article

Inorganic Chemistry

Figure 3. Plots of FSRAn‑Ni of An−Ni (An = Th, Pa, U, Np and Pu) against QTAIM data, delocalization index δ(U, Ni) and interaction energy Eint.

Figure 4. Diagram of occupied orbitals with the metal character for XU−Ni (X = Me3SiO, F, Cl, Br, and I). Note that (a) the α-spin orbital energy levels are used, (b) orbitals with similar character were marked with same color lines, and (c) energy levels for orbitals of the last four complexes were up-shifted by 0.13, 0.36, 0.40, and 0.45 eV, respectively, to make their HOMO energies equal to that of SiOU−Ni.

E


Article

Inorganic Chemistry

Figure 5. Density of states (DOSs) of An−Ni (An = Th, Pa, U, Np, and Pu), where the α-spin orbitals are plotted except for closed-shell Th−Ni.

dominated. This agrees with tetravalent uranium oxidation state with two parrelled 5f single electrons. Below them are nickel d-character HOMO-2 and HOMO-3. The other two types are related to uranium−nickel bonds and occur in relatively low-energy area. For example, SiOU−Ni has four σ(U−Ni) bonding orbitals (HOMO-7 and HOMO-13−15) and two π(U−Ni)-character ones (HOMO-8 and HOMO-9). Across the X ligands from Me3SiO, F, Cl, Br, to I, we found decreasing electron-withdrawing ability but increasing donating property. Consequently, this results in a general stability for σ/π(U−Ni) bonding orbitals, when the metal nonbonding (5f and 3d) orbitals of XU−Ni are placed in the same energy region (see the caption of Figure 4). Therefore, orbital energies imply an ITI order of Me3SiO > F > Cl > Br > I, which is consistent with results from aforementioned structural and topological analyses. Regarding anions [XU-Ni]−, HOMO, HOMO-1, and HOMO-2 are primarily of U(5f)-character. Electronic structures show that HOMO is a U(5f)-nonbonding orbital in reality and has only a very little antibonding with respect to nickel. As shown in Figure S8, other metal-involved orbitals are quite similar to those of XU−Ni. The ITI order of Me3SiO > F > Cl > Br > I is confirmed again. With respect to [U−TM]n (TM = Ni, Pd, and Pt; n = 0 and −1), electronic structures do not give a clear trend of ITI (Figures S9 and S10), due to the lack of large complex sample number (only three). When changing actinide from Th, Pa, U, Np to Pu, complexes An−Ni are given. Inspection on their density of states (DOSs) in Figure 5 obviously shows an increasing order of ITI stabilization. One can see that nickel orbitals remain almost unchanged in energy as the actinide atomic number increases, but 5f orbitals become lower and lower from Pa/U, Np to Pu. It is worth noting that Pu(5f) and Ni(3d) orbitals of Pu−Ni are even present in the same energy region. The increase in energy matching between nickel and actinide

orbitals would, in part, strength the An-Ni bond. Notably, Pa− Ni has lower-energy 5f orbital than U−Ni, but still higher than Np−Ni and Pu−Ni. In general, electronic structures of An−Ni support the increased order of ITI from Th to Pu. 3.4. Reduction Properties and ITI. The An−TM complexes investigated have various redox active sites including two metal centers, three phosphinoaryl oxide ligands and axial donor. This will make the reduction exploration complicate. In the work, we present the difference of electronspin density between reduced anion and its neutral molecule (ΔSFrag) in Table 4, and the corresponding picture is shown in Table 4. Difference in Electron-Spin Density of Each Fragment (ΔSFrag) between molecular Complex XAn-TM and One-Electron Reduced Anion [XAn-TM]−, i.e., ΔSFrag = SFrag(anion) − SFrag(molecule) n = 0 → −1

ΔSAn

ΔSTM

ΔSX

ΔS3L

[SiOU−Ni]n [FU−Ni]n [ClU-Ni]n [BrU-Ni]n [U−Ni]n [U−Pd]n [U−Pt]n [Th−Ni]n [Pa−Ni]n [Np−Ni]n [Pu−Ni]n

0.663 0.613 0.607 0.612 0.596 0.704 0.656 0.171 0.727 0.618 0.563

0.209 0.252 0.262 0.257 0.261 0.180 0.218 0.499 0.154 0.215 0.164

0.004 −0.002 0.003 0.006 0.009 0.012 0.013 0.025 0.006 0.004 0.041

0.122 0.137 0.128 0.125 0.135 0.103 0.113 0.304 0.112 0.164 0.231

Figure 6. It is clear to observe that the reduction mainly occur in the actinide center with the exception of the thorium complexes. The actinide gains about 60% reduced electron, and the transition metal and the phosphinoaryl oxides (L) have 24% and 15%, respectively. ΔSX of donor ligands is negligible due to its 0.01 average value. Th−Ni is exceptional for its Ni and L parts attain the most reduced electron density over 90%, F


Article

Inorganic Chemistry

Figure 6. Difference in electron-spin density of fragments (ΔSFrag) between molecular complex XAn−TM and one-electron reduced anion [XAn− TM]−, i.e., ΔSFrag = SFrag(anion)-SFrag(molecule), where fragments are An, TM, X and 3L.

Table 5. Calculated Electron Affinity (EA in eV) and Orbital Energies (eV) of Actinide−Transition Metal Complexes, along with Cyclic Voltammetry Data (E1/2 in V) of Experimental Complexes n = 0 → −1 a

[SiOU−Ni]n [FU−Ni]n [BG]n [BrU-Ni]n [U−Ni]n [U−Pd]n [U−Pt]n [Th−Ni]n [B]n [Np−Ni]n [Pu−Ni]n

n = 0 (Molecule)

n = −1 (Anion)

EA

E1/2b

HOMO

LUMO

HOMO

LUMO

−0.807 −0.865 −1.078 −1.110 −1.173 −1.239 −1.225 −0.706 −1.398 −1.628 −2.026

−2.50 −2.39

−2.681 −2.811 −3.042 −3.084 −3.129 −3.324 −3.268 −4.463 −3.363 −3.847 −4.120

−2.371 −2.481 −2.716 −2.749 −2.797 −2.921 −2.900 −1.964 −3.078 −3.287 −3.698

0.647 0.645 0.507 0.473 0.421 0.444 0.418 0.568 0.278 0.029 −0.253

0.938 0.967 0.947 0.922 0.883 0.909 0.831 1.235 0.567 0.760 −0.030

−2.20 −2.09 −1.92

EA = E(anion) − E(molecule), where E is total energy. Both molecular complexes and anions were optimized by the Gaussian code, and calculated energy difference corresponds to the adiabatic EA. We used EA to denote the adiabatic electron affinity in the work. bE1/2 values determined from CV from ref.16 a

with results suggested by above structural, bonding and electronic properties as well as the previous study.14 The correlation regularity built between EA and ITI also suits for U−TM (TM = Ni, Pd, and Pt), whereas changing the TM center. However, the regularity is not directly applicable to An−-Ni series complexes. As shown in Table 5, computed EA values of An−Ni approximately decrease in going from Th to Pu. If the regularity built between EA and ITI worked as XU−Ni and U−TM do, a decreased ITI stabilization order from Th to Pu would be given for An−Ni. However, this order differs from the one of Pu > Np > U > Pa > Th suggested by geometry/ QTAIM data and electronic structures. Several reasons may be possible. First, are calculations of EA reliable? To check this, we testified several factors that may affect the calculated EA values. Apart from the adiabatic EA used here, the vertical EA (marked as VEA) were computed for several uranium−nickel complexes with the Gaussian 09 program. On the basis of Gaussian-optimized geometries, various EA-related data were also calculated using the Priroda code. All these results (Table S3) indicate that the EA computation is reliable and not affected by the above factors. Second, EA values were considered for more actinide systems, [AnIV(L1)(BH4)]+/ [AnIII(L1)(BH4)] and [AnIV(L2)]/[AnIII(L2)]− for example. Therein, L1 is a dianion of heterocalix[4]arene and L2 is a

while there is 17% spin electron distribution over around Th. The effect of reduction on molecular properties has been discussed in the Supporting Information along with more detailed mechanism description. In this section, we will focus on the relationship of reduction property with ITI. Electron affinity (EA) was calculated and presented in Table 5. According to the equation for calculating reduction potential, E1/2 = −(EA+ΔGcorr)/zF, where ΔGcorr is free energy correction term, z is the number of reduction electrons, and F is Faraday constant,14,73−79 the EA value should be inversely proportional to E1/2. It is true for our calculated EA and cyclic voltammetry (CV) E1/2 values of experimentally obtained complexes16 as seen in Table 5. The good linear correlation (R2 = 0.782) between them also indicates the accuracy of current calculations. With combined theoretical and experimental results, Schelter and co-workers suggested that a decrease in the reduction potential of (OUVIX)[N(SiMe3)2]3 is attributed to stronger axial X donation to the uranium ion;14 the ITI order was given as OMe > F > Cl > Br > I. Considering the electrochemical reduction indicator EA that we used herein, it ought to have a positive correlation with the ITI stabilization. As shown in Table 5, EA values of XU-Ni show a decreasing order along OSiMe3, F, Cl, Br and I, which deduces the same order for the ITI stabilization. This conclusion is in agreement G


Inorganic Chemistry

■

tetra-anion of polypyrrolic macrocycle, and see their structures in the insets of Figure S11. One can notice in Figure S11 that the EA values decrease in going from Th to Pu, having the same trend as those of An−Ni/[An−Ni]−. These results are also consistent with the trend of experimentally measured E1/2 of AnIV/AnIII ions.7,48 So we think that it is not an inevitable regularity of the correlation between electrochemical reduction (indicated by EA or E1/2) and ITI stability. As a matter of fact, the electrochemical reduction (indicated by EA herein) involves the change between molecule and anion. It basically correlates changes of An-TM distances and QTAIM-related data upon reduction, as proved in the Supporting Information of this work. If one referred to properties of molecule or anion, energies of LUMO of molecule and HOMO of anion would have a certain relationship with EA. This is the case by inspecting orbital energies presented in Table 5. In Figure S12, a good correlation, R2 of 0.965 and 0.935, is fitted for EA against LUMO of An−Ni and HOMO of [An−Ni]−, respectively.

AUTHOR INFORMATION

Corresponding Authors

*Email: [email protected] (Q.J.P.). *Email: [email protected] (L.C.X.). ORCID

Qing-Jiang Pan: 0000-0003-2763-6976 Notes

The authors declare no competing financial interest.

■

ACKNOWLEDGMENTS This work has been supported by the National Natural Science Foundation of China (21671060 and 21273063). QJP thanks Professor Zhen-Dong Li (Beijing Normal University) for helping to improve the work. The authors are grateful to Dr. Dimitri Laikov for providing us with the Priroda code.

■

REFERENCES

(1) Denning, R. G. Electronic structure and bonding in actinyl ions. In Complexes, Clusters and Crystal Chemistry; Structure and Bonding; Springer: 1992; Vol. 79, pp 215−215. (2) Denning, R. G. Electronic Structure and Bonding in Actinyl Ions and their Analogs. J. Phys. Chem. A 2007, 111, 4125−4143. (3) O’Grady, E.; Kaltsoyannis, N. On the inverse trans influence. Density functional studies of [MOX5]n− (M = Pa, n = 2; M = U, n = 1; M = Np, n = 0; X = F, Cl or Br). J. Chem. Soc., Dalton Trans. 2002, 1233−1239. (4) Arnold, P. L.; Dutkiewicz, M. S.; Zegke, M.; Walter, O.; Apostolidis, C.; Hollis, E.; Pecharman, A.-F.; Magnani, N.; Griveau, J.C.; Colineau, E.; Caciuffo, R.; Zhang, X.; Schreckenbach, G.; Love, J. B. Subtle Interactions and Electron Transfer between U-III, Np-III, or Pu-III and Uranyl Mediated by the Oxo Group. Angew. Chem., Int. Ed. 2016, 55, 12797−12801. (5) Liddle, S. T. The Renaissance of Non-Aqueous Uranium Chemistry. Angew. Chem., Int. Ed. 2015, 54, 8604−8641. (6) Liddle, S. T. Inverted sandwich arene complexes of uranium. Coord. Chem. Rev. 2015, 293, 211−227. (7) Shi, W.-Q.; Yuan, L.-Y.; Wang, C.-Z.; Wang, L.; Mei, L.; Xiao, C.-L.; Zhang, L.; Li, Z.-J.; Zhao, Y.-L.; Chai, Z.-F. Exploring Actinide Materials Through Synchrotron Radiation Techniques. Adv. Mater. 2014, 26, 7807−7848. (8) Jones, M. B.; Gaunt, A. J. Recent Developments in Synthesis and Structural Chemistry of Nonaqueous Actinide Complexes. Chem. Rev. 2013, 113, 1137−1198. (9) La Pierre, H. S.; Michael, R.; Boris, K.; Christina, H.; Heinemann, F. W.; Liddle, S. T.; Karsten, M. Charge control of the inverse trans-influence. Chem. Commun. 2015, 51, 16671−16674. (10) Halter, D. P.; La Pierre, H. S.; Heinemann, F. W.; Meyer, K. Uranium(IV) Halide (F−, Cl−, Br−, and I-) Monoarene Complexes. Inorg. Chem. 2014, 53, 8418−8424. (11) La Pierre, H. S.; Meyer, K. Uranium−Ligand Multiple Bonding in Uranyl Analogues, [L = U=L]n+, and the Inverse Trans Influence. Inorg. Chem. 2013, 52, 529−539. (12) Kosog, B.; La Pierre, H. S.; Heinemann, F. W.; Liddle, S. T.; Meyer, K. Synthesis of Uranium(VI) Terminal Oxo Complexes: Molecular Geometry Driven by the Inverse Trans-Influence. J. Am. Chem. Soc. 2012, 134, 5284−5289. (13) Lewis, A. J.; Mullane, K. C.; Nakamaru-Ogiso, E.; Carroll, P. J.; Schelter, E. J. The Inverse Trans Influence in a Family of Pentavalent Uranium Complexes. Inorg. Chem. 2014, 53, 6944−6953. (14) Lewis, A. J.; Carroll, P. J.; Schelter, E. J. Stable Uranium(VI) Methyl and Acetylide Complexes and the Elucidation of an Inverse Trans Influence Ligand Series. J. Am. Chem. Soc. 2013, 135, 13185− 13192. (15) Gregson, M.; Lu, E.; Mills, D. P.; Tuna, F.; McInnes, E. J. L.; Hennig, C.; Scheinost, A. C.; McMaster, J.; Lewis, W.; Blake, A. J.; Kerridge, A.; Liddle, S. T. The inverse-trans-influence in tetravalent

4. CONCLUSIONS In summary, optimized structural parameters including bond lengths and formal shortness ratio (FSR) values give inverse trans influence (ITI) stabilization orders of Me3SiO > F > Cl > Br > I, Ni > Pt > Pd, and Pu > Np > U > Pa > Th, while changing ligand donor atom (X), transition metal (TM) and actinide (An), respectively. They are corroborated by QTAIM data, delocalization index, interaction energy and electronic structures. Our results agree with previous studies that reported donor ligands and a few An elements (two or three in one work) in complexes containing high-valence An and/or An−ligand multiple bonds.3,10,14,15 The current study provides a comprehensive and systematic understanding of ITI, particularly in low oxidation-state actinide-metal single bond complexes. By varying axial X donors, we also find a good correlation of the ITI stabilization with the extent of cis−U−O destabilization (reflected by calculated NBO charges) and the EA value (one important indicator for electrochemical reduction), as indicated in a previous study.14 However, it does not work for An-Ni complexes. So above molecular properties would not be a general regularity related to ITI according to the current study. An actinide-based reduction mechanism, mixed with minor TM and L, is assigned for the most complexes except for thorium−nickel ones; and the axial donor X is totally redoxinnocent.

■

Article

ASSOCIATED CONTENT

S Supporting Information *

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.inorgchem.9b01193. Figures of several correlated diagrams (Figures S1−S7 and S11−S13); curves of structural data (S14) and electron-spin density (S15); and diagrams of energetic levels of orbitals (S8−S10); tables of geometry parameters (Table S1), spin density and NBO charges (S2), various EA values (S3), QTAIM data of An−X (S4,) and comparison with uranium-group 8 metal complexes (S5 and S6); full reference of the Gaussian program and Cartesian coordinates of optimized complexes (PDF) H


Article

Inorganic Chemistry lanthanide and actinide bis(carbene) complexes. Nat. Commun. 2017, 8, 14137. (16) Hlina, J. A.; Pankhurst, J. R.; Kaltsoyannis, N.; Arnold, P. L. Metal−Metal Bonding in Uranium−Group 10 Complexes. J. Am. Chem. Soc. 2016, 138, 3333−3345. (17) Camp, C.; Toniolo, D.; Andrez, J.; Pecaut, J.; Mazzanti, M. A versatile route to homo- and hetero-bimetallic 5f-5f and 3d-5f complexes supported by a redox active ligand framework. Dalton Trans. 2017, 46, 11145−11148. (18) Kozimor, S. A.; Bartlett, B. M.; Rinehart, J. D.; Long, J. R. Magnetic exchange coupling in chloride-bridged 5f-3d heterometallic complexes generated via insertion into a Uranium(IV) dimethylpyrazolate dimer. J. Am. Chem. Soc. 2007, 129, 10672−10674. (19) Leverd, P. C.; Lance, M.; Nierlich, M.; Vigner, J.; Ephritikhine, M. Synthesis and crystal structure of homoleptic uranium hexathiolates: [NEt2H2]2[U(SPh)6] and [(Ph3P)Cu(μ-SPh)3-U(μSPh)3Cu(PPh3)]. J. Chem. Soc., Dalton Trans. 1994, 3563−3567. (20) Fortier, S.; Walensky, J. R.; Wu, G.; Hayton, T. W. High-Valent Uranium Alkyls: Evidence for the Formation of U-VI(CH2SiMe3)6. J. Am. Chem. Soc. 2011, 133, 11732−11743. (21) Napoline, J. W.; Kraft, S. J.; Matson, E. M.; Fanwick, P. E.; Bart, S. C.; Thomas, C. M. Tris(phosphinoamide)-Supported UraniumCobalt Heterobimetallic Complexes Featuring Co → U Dative Interactions. Inorg. Chem. 2013, 52, 12170−12177. (22) Ward, A. L.; Lukens, W. W.; Lu, C. C.; Arnold, J. Photochemical Route to Actinide-Transition Metal Bonds: Synthesis, Characterization and Reactivity of a Series of Thorium and Uranium Heterobimetallic Complexes. J. Am. Chem. Soc. 2014, 136, 3647− 3654. (23) Patel, D.; Moro, F.; McMaster, J.; Lewis, W.; Blake, A. J.; Liddle, S. T. A Formal High Oxidation State Inverse-Sandwich Diuranium Complex: A New Route to f-Block-Metal Bonds. Angew. Chem., Int. Ed. 2011, 50, 10388−10392. (24) Lu, E.; Wooles, A. J.; Gregson, M.; Cobb, P. J.; Liddle, S. T. A Very Short Uranium(IV)-Rhodium(I) Bond with Net Double-Dative Bonding Character. Angew. Chem., Int. Ed. 2018, 57, 6587−6591. (25) Hlina, J. A.; Wells, J. A. L.; Pankhurst, J. R.; Love, J. B.; Arnold, P. L. Uranium rhodium bonding in heterometallic complexes. Dalton Trans. 2017, 46, 5540−5545. (26) Chi, C.; Wang, J.-Q.; Qu, H.; Li, W.-L.; Meng, L.; Luo, M.; Li, J.; Zhou, M. Preparation and Characterization of Uranium-Iron Triple-Bonded UFe(CO)3− and OUFe(CO)3− Complexes. Angew. Chem., Int. Ed. 2017, 56, 6932−6936. (27) Fortier, S.; Aguilar-Calderon, J. R.; Vlaisavljevich, B.; MettaMagana, A. J.; Goos, A. G.; Botez, C. E. An N-Tethered Uranium(III) Arene Complex and the Synthesis of an Unsupported U-Fe Bond. Organometallics 2017, 36, 4591−4599. (28) Sternal, R. S.; Marks, T. J. Actinide-to-transition metal bonds. Synthesis, characterization, and properties of metal-metal bonded systems having the tris(cyclopentadienyl)actinide fragment. Organometallics 1987, 6, 2621−2623. (29) Bucaille, A.; Le Borgne, T.; Ephritikhine, M.; Daran, J. C. Synthesis and X-ray Crystal Structure of a Urana[1]ferrocenophane, the First Tris(1,1′-ferrocenylene) Metal Compound. Organometallics 2000, 19, 4912−4914. (30) Monreal, M. J.; Carver, C. T.; Diaconescu, P. L. Redox processes in a uranium bis(1,1′-diamidoferrocene) complex. Inorg. Chem. 2007, 46, 7226−7228. (31) Monreal, M. J.; Diaconescu, P. L. A weak interaction between iron and uranium in uranium alkyl complexes supported by ferrocene diamide ligands. Organometallics 2008, 27, 1702−1706. (32) Chi, X.-W.; Wu, Q.-Y.; Hao, Q.; Lan, J.-H.; Wang, C.-Z.; Zhang, Q.; Chai, Z.-F.; Shi, W.-Q. Theoretical Study on Unsupported Uranium−Metal Bonding in Uranium−Group 8 Complexes. Organometallics 2018, 37, 3678−3686. (33) Gardner, B. M.; Patel, D.; Cornish, A. D.; McMaster, J.; Lewis, W.; Blake, A. J.; Liddle, S. T. The Nature of Unsupported UraniumRuthenium Bonds: A Combined Experimental and Theoretical Study. Chem. - Eur. J. 2011, 17, 11266−11273.

(34) Gardner, B. M.; McMaster, J.; Moro, F.; Lewis, W.; Blake, A. J.; Liddle, S. T. An Unsupported Uranium-Rhenium Complex Prepared by Alkane Elimination. Chem. - Eur. J. 2011, 17, 6909−6912. (35) Patel, D.; King, D. M.; Gardner, B. M.; McMaster, J.; Lewis, W.; Blake, A. J.; Liddle, S. T. Structural and theoretical insights into the perturbation of uranium-rhenium bonds by dative Lewis base ancillary ligands. Chem. Commun. 2011, 47, 295−297. (36) Gardner, B. M.; McMaster, J.; Lewis, W.; Liddle, S. T. Synthesis and structure of {N(CH2CH2NSiMe3)3}URe(η5-C5H5)2: a heterobimetallic complex with an unsupported uranium-rhenium bond. Chem. Commun. 2009, 2851−2853. (37) Ayres, A. J.; Zegke, M.; Ostrowski, J. P. A.; Tuna, F.; McInnes, E. J. L.; Wooles, A. J.; Liddle, S. T. Actinide-transition metal bonding in heterobimetallic uranium− and thorium−molybdenum paddlewheel complexes. Chem. Commun. 2018, 54, 13515−13518. (38) Minasian, S. G.; Krinsky, J. L.; Williams, V. A.; Arnold, J. A heterobimetallic complex with an unsupported Uranium(III)Aluminum(I) bond: (CpSiMe3)3U-AlCp* (Cp* = C5Me5). J. Am. Chem. Soc. 2008, 130, 10086−10087. (39) Minasian, S. G.; Krinsky, J. L.; Rinehart, J. D.; Copping, R.; Tyliszczak, T.; Janousch, M.; Shuh, D. K.; Arnold, J. A Comparison of 4f vs 5f Metal-Metal Bonds in (CpSiMe3)3M-ECp* (M = Nd, U; E = Al, Ga; Cp* = C5Me5): Synthesis, Thermodynamics, Magnetism, and Electronic Structure. J. Am. Chem. Soc. 2009, 131, 13767−13783. (40) Liddle, S. T.; McMaster, J.; Mills, D. P.; Blake, A. J.; Jones, C.; Woodul, W. D. sigma and pi Donation in an Unsupported UraniumGallium Bond. Angew. Chem., Int. Ed. 2009, 48, 1077−1080. (41) Porchia, M.; Ossola, F.; Rossetto, G.; Zanella, P.; Brianese, N. Synthesis of triscyclopentadienyl(triphenylgermyl)uranium and facile isonitrile insertion into the uranium-germanium bond. J. Chem. Soc., Chem. Commun. 1987, 550−551. (42) Porchia, M.; Casellato, U.; Ossola, F.; Rossetto, G.; Zanella, P.; Graziani, R. Synthesis and crystal structure of triscyclopentadienyl(triphenyltin)uranium. The first example of a uranium-tin bond. J. Chem. Soc., Chem. Commun. 1986, 1034−1035. (43) Winston, M. S.; Batista, E. R.; Yang, P.; Tondreau, A. M.; Boncella, J. M. Extending Stannyl Anion Chemistry to the Actinides: Synthesis and Characterization of a Uranium−Tin Bond. Inorg. Chem. 2016, 55, 5534−5539. (44) Rookes, T. M.; Wildman, E. P.; Balazs, G.; Gardner, B. M.; Wooles, A. J.; Gregson, M.; Tuna, F.; Scheer, M.; Liddle, S. T. Actinide-Pnictide (An-Pn) Bonds Spanning Non-Metal, Metalloid, and Metal Combinations (An = U, Th; Pn = P, As, Sb, Bi). Angew. Chem., Int. Ed. 2018, 57, 1332−1336. (45) Vlaisavljevich, B.; Miró, P.; Cramer, C. J.; Gagliardi, L.; Infante, I.; Liddle, S. T. On the Nature of Actinide− and Lanthanide−Metal Bonds in Heterobimetallic Compounds. Chem. - Eur. J. 2011, 17, 8424−8433. (46) Mei, L.; Xu, C.; Wu, Q.-Y.; Hu, K.-Q.; Yuan, L.-Y.; Chen, J.; Xiao, C.-L.; Wang, S.-A.; Chai, Z.-F.; Shi, W.-Q. A neptunium(v)mediated interwoven transuranium-rotaxane network incorporating a mechanically interlocked c2 daisy chain unit. Chem. Commun. 2018, 54, 8645−8648. (47) Wang, L.; Yuan, L.; Chen, K.; Zhang, Y.; Deng, Q.; Du, S.; Huang, Q.; Zheng, L.; Zhang, J.; Chai, Z.; Barsoum, M. W.; Wang, X.; Shi, W. Loading Actinides in Multilayered Structures for Nuclear Waste Treatment: The First Case Study of Uranium Capture with Vanadium Carbide MXene. ACS Appl. Mater. Interfaces 2016, 8, 16396−16403. (48) Arnold, P. L.; Dutkiewicz, M. S.; Walter, O. Organometallic Neptunium Chemistry. Chem. Rev. 2017, 117, 11460−11475. (49) Natrajan, L. S.; Swinburne, A. N.; Andrews, M. B.; Randall, S.; Heath, S. L. Redox and environmentally relevant aspects of actinide(IV) coordination chemistry. Coord. Chem. Rev. 2014, 266, 171−193. (50) Bi, Y.-T.; Li, L.; Guo, Y.-R.; Pan, Q.-J. Heterobimetallic Uranium-Nickel/Palladium/Platinum Complexes of Phosphinoaryl Oxide Ligands: A Theoretical Probe for Metal-Metal Bonding and Electronic Spectroscopy. Inorg. Chem. 2019, 58, 1290−1300. I


Article

Inorganic Chemistry (51) Frisch, M. J.; Trucks, G. W.; Schlegel, H. B.; et al. Gaussian 09, Revision D.01; Gaussian, Inc.: Wallingford, CT, 2009. (52) Kaupp, M.; Schleyer, P. V.; Stoll, H.; Preuss, H. Pseudopotential approaches to Ca, Sr, and Ba hydrides. Why are some alkaline earth MX2 compounds bent. J. Chem. Phys. 1991, 94, 1360−1366. (53) Perdew, J. P.; Burke, K.; Ernzerhof, M. Generalized gradient approximation made simple. Phys. Rev. Lett. 1996, 77, 3865−3868. (54) Matta, C. F.; Boyd, R. J. The Quantum Theory of Atoms in Molecules; Wiley−-VCH: Weinheim, Germany, 2007; p 1−34. (55) Bader, R. F. W. Atoms in Molecules: A Quantum Theory. OUP, Oxford,: 1990. (56) Lu, T.; Chen, F. Multiwfn: A multifunctional wavefunction analyzer. J. Comput. Chem. 2012, 33, 580−592. (57) Espinosa, E.; Molins, E.; Lecomte, C. Hydrogen bond strengths revealed by topological analyses of experimentally observed electron densities. Chem. Phys. Lett. 1998, 285, 170−173. (58) Srivastava, A.; Mishra, R.; Joshi, B. D.; Gupta, V.; Tandon, P. A comparative computational study on molecular structure, NBO analysis, multiple interactions, chemical reactivity and first hyperpolarisability of imatinib mesylate polymorphs using DFT and QTAIM approach. Mol. Simul. 2014, 40, 1099−1112. (59) Noorizadeh, S.; Shakerzadeh, E. Shannon entropy as a new measure of aromaticity, Shannon aromaticity. Phys. Chem. Chem. Phys. 2010, 12, 4742−4749. (60) Cotton, F. A.; Murillo, C. A.; Walton, R. A. Multiple Bonds Between Metal Atoms, 3rd ed.; Springer: New York, 2005. (61) Pyykko, P. Additive Covalent Radii for Single-, Double-, and Triple-Bonded Molecules and Tetrahedrally Bonded Crystals: A Summary. J. Phys. Chem. A 2015, 119, 2326−2337. (62) Dutkiewicz, M. S.; Farnaby, J. H.; Apostolidis, C.; Colineau, E.; Walter, O.; Magnani, N.; Gardiner, M. G.; Love, J. B.; Kaltsoyannis, N.; Caciuffo, R.; Arnold, P. L. Organometallic neptunium(III) complexes. Nat. Chem. 2016, 8, 797−802. (63) Kirker, I.; Kaltsoyannis, N. Does covalency really increase across the 5f series? A comparison of molecular orbital, natural population, spin and electron density analyses of AnCp3 (An = ThCm; Cp = η5-C5H5). Dalton Trans. 2011, 40, 124−131. (64) Huang, Q.-R.; Kingham, J. R.; Kaltsoyannis, N. The strength of actinide-element bonds from the quantum theory of atoms-inmolecules. Dalton Trans. 2015, 44, 2554−2566. (65) Kaltsoyannis, N. Does Covalency Increase or Decrease across the Actinide Series? Implications for Minor Actinide Partitioning. Inorg. Chem. 2013, 52, 3407−3413. (66) Arnold, P. L.; Prescimone, A.; Farnaby, J. H.; Mansell, S. M.; Parsons, S.; Kaltsoyannis, N. Characterizing Pressure-Induced Uranium CH Agostic Bonds. Angew. Chem., Int. Ed. 2015, 54, 6735−6739. (67) Mountain, A. R. E.; Kaltsoyannis, N. Do QTAIM metrics correlate with the strength of heavy element-ligand bonds? Dalton Trans. 2013, 42, 13477−13486. (68) Tassell, M. J.; Kaltsoyannis, N. Covalency in AnCp4 (An = ThCm): a comparison of molecular orbital, natural population and atoms-in-molecules analyses. Dalton Trans. 2010, 39, 6719−6725. (69) Wu, Q.-Y.; Wang, C.-Z.; Lan, J.-H.; Xiao, C.-L.; Wang, X.-K.; Zhao, Y.-L.; Chai, Z.-F.; Shi, W.-Q. Theoretical Investigation on Multiple Bonds in Terminal Actinide Nitride Complexes. Inorg. Chem. 2014, 53, 9607−9614. (70) Wang, C.-Z.; Gibson, J. K.; Lan, J.-H.; Wu, Q.-Y.; Zhao, Y.-L.; Li, J.; Chai, Z.-F.; Shi, W.-Q. Actinide (An = Th-Pu) dimetallocenes: promising candidates for metal-metal multiple bonds. Dalton Trans. 2015, 44, 17045−17053. (71) Wu, Q. Y.; Lan, J. H.; Wang, C. Z.; Cheng, Z. P.; Chai, Z. F.; Gibson, J. K.; Shi, W. Q. Paving the way for the synthesis of a series of divalent actinide complexes: a theoretical perspective. Dalton Trans. 2016, 45, 3102−3110. (72) Chen, F.; Qu, N.; Wu, Q.; Zhang, H.; Shi, W.; Pan, Q. Structures and Uranium-Uranium Multiple Bond of Binuclear

Divalent Uranium Complex of Pyrrolic Schiff-base Macrocycle: a Relativistic DFT Probe. Huaxue Xuebao 2017, 75, 457−463. (73) Qu, N.; Zhong, Y.-X.; Schreckenbach, G.; Pan, Q.-J. A computational investigation of polypyrrolic macrocyclic actinyl complexes: effects of explicit solvent coordination on structure, vibrational spectra and redox property. Theor. Chem. Acc. 2016, 135, 196. (74) Graves, C. R.; Yang, P.; Kozimor, S. A.; Vaughn, A. E.; Clark, D. L.; Conradson, S. D.; Schelter, E. J.; Scott, B. L.; Thompson, J.; Hay, P. J.; et al. Organometallic Uranium (V)− Imido Halide Complexes: From Synthesis to Electronic Structure and Bonding. J. Am. Chem. Soc. 2008, 130, 5272−5285. (75) Elkechai, A.; Mani, Y.; Boucekkine, A.; Ephritikhine, M. Density Functional Theory Investigation of the Redox Properties of Tricyclopentadienyl- and Phospholyluranium(IV) Chloride Complexes. Inorg. Chem. 2012, 51, 6943−6952. (76) Steele, H. M.; Guillaumont, D.; Moisy, P. Density Functional Theory Calculations of the Redox Potentials of Actinide(VI)/ Actinide(V) Couple in Water. J. Phys. Chem. A 2013, 117, 4500− 4505. (77) Zhao, H.-B.; Zheng, M.; Schreckenbach, G.; Pan, Q.-J. Could new U(ii) complexes be accessible via tuning hybrid heterocalix[4]arene? A theoretical study of redox and structural properties. Dalton Trans. 2018, 47, 2148−2151. (78) Bi, Y.-T.; Zhong, Y.-X.; Zhou, B.-B.; Pan, Q.-J. Pacman-Like Alkaliated Actinyl Complexes of a Polypyrrolic Macrocycle: A Relativistic DFT Study. ChemistrySelect 2017, 2, 6801−6810. (79) Tian, J.-N.; Zheng, M.; Li, L.; Schreckenbach, G.; Guo, Y.-R.; Pan, Q.-J. Theoretical investigation of U(i) arene complexes: is the elusive monovalent oxidation state accessible? New J. Chem. 2019, 43, 1469−1477.

J


Inverse Trans Influence in Low-Valence Actinide ... - ACS Publications

Recommend Documents